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Vapour pressure

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Reference
Endpoint:
vapour pressure
Type of information:
experimental study
Adequacy of study:
key study
Study period:
June - August 2018
Reliability:
1 (reliable without restriction)
Qualifier:
according to guideline
Guideline:
OECD Guideline 104 (Vapour Pressure Curve)
Qualifier:
according to guideline
Guideline:
EU Method A.4 (Vapour Pressure)
GLP compliance:
yes
Type of method:
effusion method: isothermal thermogravimetry
Specific details on test material used for the study:
Hexamidine di isethionate batch 42964
Key result
Test no.:
#1
Temp.:
20 °C
Vapour pressure:
< 0 Pa
Remarks on result:
other: 1.36x10e-18 Pa

Reference Items:

Chrysene

Hexachlorobenzene

Naphthalene

Water for analysis

Determination of the Regression Curve by Analysing Reference Items:

The measurement of the reference compounds and the setup of the relationship between the vapour pres-sure and the evaporation rates were performed at least once every year. The last reference test was done from January 09 to January 18, 2018.

Reference Item Preparation:

One reference item at a time was applied to the surface of a rough-ened glass plate in a homogeneous layer.

Measurement:

The plate was placed in the TGA instrument. The weight loss of the reference item was measured continuously as a function of time at four different temperatures at constant nitrogen flow.

The following temperature program was used.

Start temperature: minimum 10 °C

Temperature increase: 10 °C (with ramp 10 °C/min)

Isothermal interval: 5 or 10 min

End temperature: maximum 180 °C

Repeatability:

At least three replicates

Conclusions:
The isothermal thermogravimetrical effusion method was applied for the determination of the vapour pressure of Hexamidine dii-sethionate.
A value of the vapour pressure of the test item was determined using the data obtained between 220 °C and 250 °C.
The vapour pressure of the test item was estimated to be smaller as 10E-10 Pa at 20 °C (1.36 x 10E-18 Pa).
Executive summary:

According to Study 17/218-909AN, the melting range of the test item is 215 °C to 217 °C. The evaluation of the vapour pressure was done with the reproducible weight loss values above > 1 μg/min in the temperature range between 220 °C to 250 °C (above the melting point).

The resulting equation was:

logPT=C+D x log VT

log PT=4.3781+1.0022 x log VT ( The coefficient of correlation (R2) was 0.9825)

and Evaporation Rate Curve: log VT=a x 1000/T+b

Inserting the equation for log VT above, the following equation for the temperature dependence of the vapour pressure of the test item is obtained:

log PT=C+D x (a x 1000/T +b)= C+(D x b)+(D x a x 1000 )/T

(where: a = -13.2535, b =23.0394, with The coefficient of correlation (R2) was 0.9884 and C = 4.3781 and D = 1.0022)

With this equation, a following vapour pressure results were obtained: 1.36 x 10e-18 Pa at 20 °C.

Description of key information

Key value for chemical safety assessment

Vapour pressure:
0 Pa
at the temperature of:
20 °C

Additional information